The small second has an exceptionally long post, which is impossible to find. By now I ordered long post second hands with three different suppliers and I gave up
On the left is the original (broken) second hand and on the right is what I have found so far with JB and O.Frei. Missing 0.7mm

Can you explain what you mean in more detail. It sounds like a great idea for future use and would like to know a bit more about how. I think it's the arm that's confusing me.

Do you narrow the part with the hand (crush? cut slits in upper pipe to make it easier to narrow/fit inside the lower pipe?) then stick it into a long pipe (with no hand) and then affix the two (crush or push onto the lower?). Sorry for all the crushing but that seems like the quickest hack that will make many people cringe with an "oh no...." reaction :

I can probably help out with at least the second hand Thojil. I bought a 415CA that looked to be in good shape but it had some problems and so over the years I've picked up an addition two not working ones for parts. They are now at the watchmaker with the hopes that he can make a good working one. When I get them back I'll be in touch to see if you are still looking for the parts.

Kind of yes. I wondered that, if the barrels were the same diameter, was it possible to remove the hand from an existing seconds hand unit and transplant it onto the long barrel.

I received the parts that Kastner was so kind to donate and found the time last weekend to work on the second hand. Unfortunately Kaster had an incomplete second hand, missing its post. Nothing to loose, so I tried what was suggested here already and removed the post from the original hand and fitted it to Kastner's hand.

As the new hand apparently separated from its post without damaging it, I first tried to pull off the old hand. No movement at all, so I went for more a drastic approach and sanded down the flanged edge of the post until I could remove the old hand.

The remaining stub was long enough to hold the new hand and required just a few light taps to fit. Just to be sure, I put a tiny drop of super glue on the back side to secure the hand, but don't think it was necessary. Don't know what will happen if I ever try to remove the hand again

Below some pictures and the final result including Kastner's new month disc. The dial is a redial by Int. Dial, which is one of the lesser results of the redials they have done for me. I rejected the result twice and even at their 3rd attempt they got the date numbers 8-23 upside down. I gave up... The photo is a bit overexposed, but the final result when sitting in its case is pretty good.